Post-operative pressure lability and cardiac baroreflex in normotensive patients as a function of age.

BACKGROUND: Pressure lability may be linked to the loss of the cardiac baroreflex. The reduction of the sensitivity of the cardiac baroreflex has not been delineated in the post-operative period according to age in normotensive patients. This study addresses pressure lability and slope of the cardiac baroreflex as a function of age.
METHODS: Patients were allocated to the following three groups: young (20-39 years, n=7), middle aged (40-59 years, n=7) and elderly (60-79 years, n=6), and studied before minor intra-abdominal surgery under CO(2) peritoneal insufflation and nitrous oxide-isoflurane-sufentanil anesthesia, up to 24 h after extubation. An electrocardiogram and non-invasive beat-by-beat pressure monitoring (Finapres) allowed offline calculation of the sensitivity of the cardiac baroreflex ('sequence' technique) and standard deviation (SD) of heart rate (HR; HR variability) and systolic blood pressure (SBP; pressure lability).
RESULTS: Before anesthesia, (a) an inverse relationship was observed between the slope of the cardiac baroreflex and age and (b) a trend (P<0.09) existed between the slope of the cardiac baroreflex and pressure lability, irrespective of age. During the early post-operative period, young patients returned to their baseline slope of the cardiac baroreflex; no inverse relationship between increased SD of SBP and decreased SD of RR interval was observed. Middle-aged and elderly patients displayed a depressed slope of the cardiac baroreflex both before and after anesthesia.
CONCLUSION: At variance with the pre-operative period, no simple inverse relationship was observed between increased pressure lability and depressed HR variability in young patients during the early post-operative period.